Method and apparatus for forming flat-sided tubing



Jan. 21, 1941.

L. M. KURTZ ZEEAZ METHOD AND APPARATUS FOR FORMING'FLAT-SIDED TUBING Filcdsept. 28, 2.93%

vento Lowell Kfitz,

HIS Att y Patented Jan. 21, 1941 PATENT OFFICE METHOD AND APPARATUS FOR FORMING FLAT-SIDED TUBING Lowell M. Kurtz, Scotia, N. Y., assignor to General Electric Company,

York

a corporation of New Application September 28, 1939, SerialNo. 298,931

My invention relates to methods and apparatus for forming flat-sided tubing or tubing with a rectangular cross-section; and particularly to a method and apparatusfor forming such tubing. from tubing 01' round cross-section.

In the design of fluidcirculating apparatus, it is frequently desirable to provide conduits having fiat sides. For example, in heat exchangers such as those sometimes employed in refrigerating machines, it is necessary to provide as much area of contact as possible between the conduits conveying fluids at difierent temperatures in order to eflfect the maximum transfer of heat. When one conduit is wound around another as is frequently done in practice, it is desirable that i the wound conduit be flattened to provide increased contact area, and it is common practice to provide flat conduits or conduits of rectangular cross section for this such conduit is relatively high and a saving in cost may be efiected by suitable flattening of the conventional round conduit. However, considerable diiilculty has been encountered because of the tendency of theround conduit to buckle 20 and preventthe formation of a flat side area. Accordingly, it is an object of my invention to provide an improved method for forming flat-.

sided or duit. o o

Another object of my invention is to provide an improved apparatus for forming a fiat-sided rectangular conduit from round conor rectangular. conduit from conduit of round cross-section. Another object ofmy invention is to provide 33 an improved apparatus and method for forming a helix of tubing of substantially rectangular cross-section from roundtubing so that the helix may surround another tube or conduit and provide a greatly increased area of contact.

Further objects and advantages of my invention willbecome apparent as the following description proceeds,'and the features of novelty which characterize out with particularity in the claims annexed to and forming a part of this specification. Fora better understanding of my invention,

larged sectional views on lines 4-4, [-5, 6 6 as 1+1 and 8-8, respectively, of Fig. 2, the sec stock maybe adjusted. by rotation purpose. The cost of' my invention will be pointed between the 9 Claims. ((1153-47) tions in Figs. 6, 7 and 8 being further enlarged.

shown a machine or apparatus arranged to form a helical conduit in from tubing stock or conduit of round cross-section in such a manner that the cross-section of the conduit i0 is rectangular.

tionary headstock l2 and a movable carriage I3, the position of which with respect to the headof the hand wheel I l. fI'he carriage may be driven'by a threaded shaft l5 through a suitable clutch actuated by a handle IS. The helical conduit I 0 is formed on an arbor The inplaceby a threaded bolt 21. tion 26 is a guide passage "having a width equal to that of the round tubing indicated at 29 and the upper portion of which is .curved to conform to the curvature oi the round tubing, as clearly shown in Fig. 4. The portion of the tool 23 tool holder and the arbor is constructedvto form a tube flattening die and is pro- 33 conforming to the curvature I3 will vary according to the vided with a removable section 30 so that the round tubing may be inserted in the tool and then flattened in the die portion of the tool by tightening of a pair of bolts 3| which secure the portion 30 to the remainder of the tool 23. When the, tubing has once been secured in place in the tool and the tool is in position over the first turn of the arbor H, the end of a length of tubing protruding beyond the tool 23 may be secured to the chuck l8 by a clamp 32 so that upon rotation of the chuck and arbor, the tubing will be drawnthrough the tool 23 and wound on the arbor. It will be noted that the tool 23 is arranged to guide the tubing until it is adjacent the arbor and is provided with a cut-away portion of the arbor. The flattened portion of the tubing within the tool 23 is indicated at 34 and it will be noted in Fig. 2 that the lower edge of this portion moves in a path tangentially of the arbor so that it intersects the arbor since the shortest distance between the path and the axis of the arbor is less than the radius of the arbor. The tool 23 holds the tubing rigidly in this position and as the arbor is rotated the tubing is drawn tightly thereon and is compressed in a direction substantially normal to the plane of the flattened portion 3. The tubing is fed on the arbor at such a rate that it is maintained at all times directly over the helical groove IS.

The width of the groove 19 is somewhat lessthan the desired width of the finished fiat side of the conduit which is to be formed onthe arbor. The groove is counteracts the tendency of the tubing to buckle as it is wrapped on the arbor and facilitates the formation of a flat surface on the tubing adjacent the arbor. It will be understood that the term "flat as used in this application has particular reference to the flattening of the cross-section of the tubing since it is ob vious that the surface formed within the helical section of the tubing is cylindrical and not in a single flat plane.

Successive steps in the formation of the straight-sided tubing from the round tubin stock are illustrated in Figs. 4 to 8 inclusive. Fig. 4 shows the cross-section of the stock within the passage 28 of the tool. Fig. 5 shows the crosssection of the tubing after it has been flattened to form the portion 34. Fig. 6 shows the tubing being compressed just as it leaves the tool 23 and engages the arbor II, it being noted that the curvature of the cross-section of the tubing 34 has been somewhat flattened adjacent the arbor. Fig.6 also shows clearly the cross-section of the groove is. Fig.7 shows the further widening and flattening of the cross-section of the tubing as it leaves the tool and is being wrappedtightly on the arbor, the corners or contacting portions of thetubing having moved outwardly toward the sides or the groove l9; and Fig. 8 shows the final cross-section of the helical conduit l with the edges ofthe tubing resting on the arbor outside the groove It. It is to be noted that the change of shape of the cross-section of the tubing is ef- Iected within a fraction of a turn of the arbor after the tubing has left the tool 23. The flat side of the cross-section shown in Fig. it lies directlyover the groove l9 and the opposite or top side has also been flattened due to the inherent effect of the winding operation. It will be readily understood that the dimensions of the groove weight and dimensions of the round tube stock from which the square tube is to be made. The most desirable shape and size of the groove for a given size of tubing may be determined readily by trial.

From the foregoing, it is apparent that I h provided a. simple and effective method and apparatus for producing conduit or rectangular or fiat-sided cross-section from round tubing stock, and that this improved method and apparatus may be-employ ed in a wide range of applications.

While I have illustrateddand. described my invention in connection with a particular apparatus and article, other applications will readily be apparent to those skilled in the art. I do not, therefore, desire my inventign to be limited to the particular -methodand construction illustrated and described and I intend in the accompanying claims to cover all embodiments within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is: s

l. The method of forming tubing of substantially rectangular cross-section from round tubing which comprises partially flattening a length of round tubing to provide tubinghaving a crosssection with two substantially flat sides and two round sides, and thereafter pressing one of said round sides inwardly toward the center of the tubing along lines moving progressively apart as the sidej of, the tubing is flattened until the desired width of the finished tubing has been obtained.

' 2. The method of forming tubing having a cross-sectionwith at least one flat side from tubing having a cross-section with around side which comprises providing an arbor having a groove around the periphery thereof, said groove having a width less than the desired width 'of the flat side of the finished tubing, and winding a length of the tubing having a round side onto the arbor with the round side of the cross-section thereof centered over the groove in the arbor whereby the compression of the tubing against the arbor flattens the round side thereof.

3. The method of forming tubing of substantially rectangular cross-section fromgtubing of round cross-section which comprises compressing a length of tubing 0! round cross-section to provide tubing of elongated cross-section, an arbor with a shallow groove of rounded crosssection around the periphery thereof, the groove having a. width less than the desired width of a side of the finished tube, and winding the compressed length of tubing onto the arbor over the groove therein and with the longitudinal axis of the cross-section'of the tubing substantially normal to the axis of the arbor, whereby the side of the tubing adjacent the arbor is flattened.

4. The method of forming tubing of substantially rectangular cross-section from tubing of round cross-section which comprises compressing a length of tubing of round cross-section to provide tubing of elongated cross-section; pro-- viding an arbor with a groove around the periphery thereof, the groove having a width less than the desired width of a side of the finished tubing; guiding the compressed length of tubing toward the arbor in alignment with the groove therein, with the longitudinal axis of the compressed section of said tubing substantially normal to the axis of the arbor, and with the shortest distance between the extended path of the providin tubing and the axis of the arbor less than the tially rectangular 5. The method of forming from round tubing the cross-section of which is the arbor. 6. The method of forming tubing of substancross-section from round tub ing which comprises providing an arbor with a groove around the periphery thereof, the groove having a width less than the desired width of a side of the finished tube, and partially flattening the tubing and winding it onto the arbor over the tion thereof substantially normal to the arbor whereby the side of the tubing adjacent the arbor y is flattened.

7. Apparatus for forming flattened tubing train tubing of round cross-section including an arbor alignment with said having a groove therein, the width of the groove and for guiding the tubing groove. 9. Apparatus for substantially square cross-section from round tubing which includes a rotatable arbor having a roove forming a helix of tubing of 

